Question

Calculate ΔrG∘ at 298 K for NH3(g)+HBr(g)→NH4Br(s)

Answer 1

The standard reaction Gibbs free energy change (ΔG°) for the reaction NH3(g) + HBr(g) → NH4Br(s) at 298 K is calculated using the relationship ΔG° = ΔH° - TΔS°. The given standard enthalpy change is -483.652 kJ/mol, and the standard entropy change needs to be obtained from a data table to complete the calculation.

Step-by-step explanation:

To calculate the standard reaction Gibbs free energy change (ΔG°) for the reaction NH3(g) + HBr(g) → NH4Br(s) at 298 K, we use the relationship ΔG° = ΔH° - TΔS°, where ΔH° is the standard enthalpy change and ΔS° is the standard entropy change of the reaction. Given that ΔH° is -483.652 kJ/mol, we will also need the standard entropy change ΔS° (not provided here) to calculate ΔG°.

To proceed with the answer, the value of ΔS° needs to be sourced from a reliable data table such as Appendix G mentioned in the question prompts. Once ΔS° is known in J/(mol·K), the equation becomes:

ΔG° = (-483.652 kJ/mol) - (298 K)(ΔS° in J/(mol·K))(1 kJ/1000 J)

Note that it is important to convert the entropy change from J to kJ by dividing by 1000 due to the units of ΔH° being in kJ/mol. The resulting ΔG° will yield the standard Gibbs free energy change for the reaction at 298 K.

Answer 2

You need information that you haven't provided in the question. Perhaps your text has a table of ΔGof for these compounds. In that case,

ΔGorxn = Sum of ΔGof products - ΔGof reactants

Just plug in the values that you find and calculate the free energy change of the reaction